Poration



Patented Aug. 28, 1928.

UNITED STATES 1,682,242 PATENT OFFICE.

WALTER A. PATRICK, OF BALTIMORE, MARYLAND, ASSIGNOR TO THE SILICA GELGOR- PORATION, 0F BALTIMORE, MARYLAND, A CORPORATION OF MARYLAND.

METHOD OF MAKING TITANIUM-OXIDE GELS.

No Drawing. Original application filed February 18,1921, Serial No.446,108. Divided and this application filed Kay 24, 1924. Serial No.715,780.

The present application which is a division of my application 446,108filed February 18, 1921 relates to a method of making an adsorbent andcatalytic gel of titanic oxide.

In my Patent 1,297,724 for silica gel and ,process of making the same Idisclosed and claimed a new method of producing hard porous highlyadsorbent gels. The spe c1 fic example mentioned in the patent is sillcael.

5 Prior to my patent the only known way of producing gels employed theslow and impractical step of dialysis. This was a laboratory method andwould never have permitted the manufacture of gels in such quantitlesand cheap enough, so that they could be employed in the arts. My patentabove mentioned describes how to avoid this step and manufacture gelscheaply and quickly so that they can be utilized in many fields.

The present invention relates to another species of the inventiondisclosed in the patent. More specifically, it isdirected to a method ofproducing the gel of titanic oxide either as such or in combination withone or more of the oxides of aluminum, tungsten or tin.

The principal object of the invention is to produce a gel of titanicoxide either alone or combined with other colloidal oxides possessinggreat adsorbing powers, and by a method which is commerciallypracticable.

For the method of the present invention, I carefully determine theconcentrations of an acid solution and a solution of a soluble salt,such as a sodium salt of the acid of titanic oxide, such that whenmixed, will set to a hydrogel within four or five hours after mixing.Great care must be exercised in bringing the acid and salt solutionstogether, in order to avoid a rapid coagulation. To prevent thiscoagulation it is necessary to vigorously stir the solutions at themoment of mixing. The amounts of the salt solution and the acid solutionused are such as to give a final concentration of the H ions coming fromthe acid in the mixture varying between one-tenth and five-tenths ,molsper litre. The salt solution should preferably be of a concentration offrom 3% to 7 by weight. Care should be taken to add the salt solution tothe acid solution, or to bring them together simultaneously. If the acidsolution is added to the salt solution the result will be a failure.

Thus for the production of titanic oxide gel, 0. 3% to 7% solutionofsodium titanate is added to an acid solution, for example hydrochloricor sulphuric acids, until the concentration of the hydrogen ions comingfrom the acid in the mixture is from onetenth to five-tenths mols perlitre, and preferably about one-tenth to two-tenths mols per lltre. Thesodium titanate and acid solutions are thoroughly stirred at the time ofmixing to prevent premature coagulation. The mixture sets to a hydrogelin a short tune and is then broken into pieces and moisture removed asdirected hereinafter.

The temperature of the solutions during the time of mixing and settingis an important factor in the time required for the setting of thehydrogel. At a temperature of about C. the mixture; sets to a hydrogelin thirty minutes to one hour and the product is ust as good as the gelformed by mixing the solutions at a lower temperature but requiring aconsiderably longer time to set. Usually solutions at the time ofmixingand at the time of setting are at atmospherlc temperature butsatisfactory results may be obtained at temperatures from 15 C. to 80 C.On mixing the acid and the soluble salt solutions, a colloidal solutlonof the acid corresponding to the oxide is first formed. It is from thissolution that the compound sets to a hydrogel. The hydrogel which isformed by allowing the mixture to set is then broken into pieces andwashed free from acid and salt. If; the wash water is heated this stepis expedited. The washed hydrogel must now have its moisture removed toobtain the hard gel. WVhen this is effected by drying, it is essentialthat the water be removed slowly, as the resulting finely porouscondition of the gel obtained depends upon the proper drying of thehydrogel. To this end the hydrogel is first dried in a stream of air at75 C. to 120 C. After this heating the gel will still contain aconsiderable quantity of water and the greater part of this is drivenoff by increasing the temperature slowly up to 300 C. to 400 C. It may,however, be dried at 120 C. but this will take longer. In a general wayit may be said that not all the Water should be driven out of the gel.v

The resulting product is a most stable substance which can; be safelyheated to relatively high temperatures such as 700 C. without fear ofinjury. The method of drying may be modified by taking the materialafter the first heating step as above described, and subjecting the sameto a vacuum to further remove the Water, the temperature during thisvacuum treatment being from 75 C. to 120 C. The product obtained by thismethod is just as stable as if the water had been removed by a furtherheating up to 300 C. to 400 C. The gel which is dried in a vacuum isalso stable to relatively high temperatures, such as 700 C.

The final product is a hard, transparent substance very closelyresembling glass in appearance. When prepared in the above manner it isvery porous, the pores being ultra-microscopic and of exceedingly finedimensions. It is because of this fine porous structure that the gel issuch an efiicient ad-- sorbing medium. The hardness which the gelpossesses is a desirable property for the reason that the gel willretain its shape and structure and not crumble or pack when placed in avessel for the purpose of adsorbing fluids.

In the foregoing description it was-stated that a solution of the sodiumsalt of the acid corresponding to the oxide is employed. It is to beunderstood, however, that any soluble salt of the acid corresponding tothe oxide may be employed. The gel prepared in accordance with thisinvention, in addition to being an eflicient adsorbent of fluids,

also possesses marked catalytic activity.

By mixing solutions of a soluble salt of the acid of titanic oxide andsoluble salt of the acid of one or more of the oxides of aluminum,tungsten or tin, a gel will be obtained which may be termed a pluraloxide gel. The concentrations and quantities of the solutionsv aredetermined as already described, and the hydrogel formed by the mixturemay have its moisture removed by drying as previously set forth. In thismanner plural gels of any number of combinations of said oxides may beobtained. For example a plural gel of titanic oxide and tungstic oxidemay be obtained by mixing with vigorous stirring 3% to 7% solutions byweight of sodium titanate and sodium tungstate, and a solution of anacid, for example hydrochloric acid until the hydrogen ions in themixture have a concentration of one-tenth to five-tenths mols per litre.Then the mixture is allowed to set to a hydrogel, broken into pieces anddried as described herein.

Having thus described the invention what is claimed as new and'desiredto be secured by Letters Patent is:

1. In the process of preparing titanic oxide gel, the step of addingwith thorough stirring a 3% to 7% solution of a soluble titanate to anacid solution, the amounts of the tltanate and acid solutions and theconcentration of the acid solution being such that the finalconcentration of the H ions resulting from the acid in the mixture isfrom one-tenth to five-tenths mols per litre.

2. In the process of reparing titanic oxide gel, the step of ad stirringa soluble titanate solution to an acid solution, the amounts andconcentrations of said solutions being such that the final concentrationof H ions resulting from the acid in the mixture is from one-tenth tofive-tenths mols per litre.

3. The process of preparing titanic oxide gel consisting in adding withthorough stir ring a soluble titanate solution to an acid solution, saidsolutions being of such concentrations and amounts that the finalconcentration of H ions resulting from the acid in the mixture is fromone-tenth to five-tenths mols per litre, whereupon after a time themixture will set to a hydrogel without removal of any of the excess acidand salt, thereafter Washin" said hydrogel to remove the acid and sa t,and removing most of the water from the resulting product.

4. The process of preparing titanic oxide gel consisting in adding withthorough stirring a 3% to 7% solution of sodium titanate to a solutionof an acid, the concentration of the acid and the amounts of thesolutions being such that the final concentration of H ions resultingfrom the acid in the mixture is from one-tenth to five-tenths mols perlitre, whereupon the mixture, after a time, sets to a hydrogel withoutremoval of any of the excess acld and salt, washing the hy drogel toremove acid and salt, and removing most of the water'from the resultingproduct.

5. The process of preparing titanic oxide gel consisting in adding withthorough stirring a soluble titanate solution to an acid solution, saidsolutions being 'of such amounts and concentrations that the finalconcentration of H ions resulting from the acid in the mixture is fromone-tenth to five-tenths mols per litre, whereupon, after a time, themixture sets to a hydrogel, washing said hydrogel to remove acid andsalt, drying the h'drogel at a. temperature of 75 to 120 to drive off apart of the moisture and then slowly increasing the temperature to driveoff the greater part of the remaining moisture.

ding with thorough ide will set to a hydrogel without removal of any ofthe excess acid and salts, washing to remove acid and salts and dryingto remove most of the water from the resulting product.

7. A plural Oxide gel being a hard glassy material havingultra-microscopic pores, stable in the presence of air up to hightemperatures, and consisting of titanic oxide and one or more colloidaloxides.

8. In the process of preparing titanic, oxide gel, the steps of allowinga colloidal solution of titanic acid to set to a hydrogel, drying theh-ydrogel in a current of air heated to 75 C. to 120 C. and then slowlyincreasing the temperature.

9. In the process of preparing titanic oxide gel, the steps of allowinga colloidal solution of titanic acid to set to a hydrogel,

drying the hydrogel in a current of air. heated to 7 5 C. to 120 C. andthen slowly increasingthe temperature to 300 to 400 10. In the processof preparing titanic oxgel the steps of allowing a colloidal titanicacid solution to set to a hydrogel, dryi the hydrogel in a current ofair heated to to 120 C. and then slowly increasing the temperature to apoint not exceeding 400 C. I

11. In the process of preparing titanic oxide gel, the steps of allowinga colloidal 1 solution of titanic acid to set to a hydrogel,

drying the hydrogel in a current of air heated to 75 to 120 C.,subjecting the gel to a vacuum and then further heat-ing the gel.

12. The process of preparing a plural oxide gel containing titanic oxideconsisting in adding with thorough stirring 3% to 7% solutions of -asoluble titanate and soluble salts of the acids of the other oxides toan acid, the solutions being of such concentrations and amounts that thefinal concentration of H ions resulting from the acid in the mixture isfrom one-tenth to five-tenths mols per litre, whereupon, after a time,the mixture will set to a hydrogel without removal of any of the excessacid and salts, washing to remove acid and salts and drying to removemost of the water from the re-' sulting product.

In testimony whereof I hereunto aflixmy signature.

WALTER VA. PATRICK.

